This invention relates to the field of medical devices, and more particularly to a guidewire for advancing a catheter within a body lumen in a procedure such as percutaneous transluminal coronary angioplasty (PTCA).
In a typical PTCA procedure a guiding catheter having a preformed distal tip is percutaneously introduced into the cardiovascular system of a patient by means of a conventional Seldinger technique and advanced therein until the distal portion of the guiding catheter is located within the patient's ascending aorta with distal tip of the guiding catheter seated in the ostium of a desired coronary artery. A guidewire is positioned within an inner lumen of an over-the-wire dilatation catheter and then both are advanced through the guiding catheter to its distal end. The guidewire is first advanced out of the distal end of the guiding catheter into the patient's coronary vasculature until the distal end of the guidewire crosses a lesion to be dilated. Then the dilatation catheter, having an inflatable balloon on the distal portion thereof, is advanced into the patient's coronary anatomy over the previously introduced guidewire until the balloon of the dilatation catheter is properly positioned across the lesion. Once in position across the lesion, the balloon is inflated one or more times to a predetermined size with liquid at relatively high pressures (e.g. greater than 4 atmospheres) to compress the arteriosclerotic plaque of the lesion against the inside of the artery wall and to otherwise expand the inner lumen of the artery. Generally, the inflated diameter of the balloon is approximately the same as the natural diameter of the body lumen being dilated. Inflation to a diameter smaller than the natural diameter will result in and incomplete dilatation and inflation to a diameter larger than the natural diameter can result in damage to the arterial wall. After the balloon is finally deflated, blood flow resumes through the dilated artery and the dilatation catheter can be removed therefrom.
The lesion or lesions to be dilated within the patient's coronary artery may be located from a few centimeters up to about 20 cm or more from the distal end of the guiding catheter which is seated in the patient's coronary ostium. This requires the guidewire to be extendable for up to 25 cm or more from the distal end of the guiding catheter because the distal end of the guidewire must extend well beyond the lesion to be dilated so that the dilatation balloon on the distal end of the catheter can be properly positioned within the stenotic region.
Conventional guidewires for angioplasty and other vascular procedures usually comprise an elongated core member with one or more smaller diameter sections near the distal end thereof and a flexible body such as a helical coil disposed about the distal portion of the core member. A shapable member, which may be the distal extremity of the core member or a separate shaping ribbon secured to the distal extremity of the core member, extends through the flexible body and is secured to a rounded plug at the distal end of the flexible body. Torquing means are provided on the proximal end of the core member to rotate, and thereby steer, the guidewire while it is being advanced through a patient's vascular system.
A major requirement for guidewires and other guiding members, whether they be solid wire or tubular members, is that they have sufficient column strength to be pushed through a patient's vascular system or other body lumen without kinking. However, the distal section of the guidewire must be flexible enough to avoid damaging the blood vessel or other body lumen through which it is advanced. Efforts have been made to improve both the strength and flexibility of guidewires to make them more suitable for their intended uses, but these two properties tend to be diametrically opposed to one another, in that an increase in one usually involves a decrease in the other. There has been a gradual decrease in the profiles or transverse dimensions of commercially available intravascular catheters and guidewires particularly for use in coronary arteries. However, concomitant with the decrease in profile has been a loss in pushability. Stiffening members have been employed with catheters but they have complicated the procedures of use, because the stiffening member usually would have to be removed from an inner lumen of the catheter in order for the inner lumen to be utilized, e.g. for inflating the balloon or advancing a guidewire therethrough. Stiffening members have also increased the complexity of the manufacturing process for dilatation catheters.
What has been needed and heretofore unavailable is a guidewire which is particularly suitable for use in an over-the-wire dilatation catheter system with a very flexible distal portion to facilitate advancement within a patient's coronary anatomy and a proximal portion with greater pushability. The present invention provides a guidewire and a dilatation catheter system including the guidewire which provides such a desirable combination of such properties.